JPS5938474B2 - Safety device for ventilation of automobile fuel tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a safety device for ventilation of fuel tanks, especially in motor vehicles.

The problems posed by fuel tank ventilation are well known.

In practice, an exchange of gases in both directions must take place between air and fuel, so that, as the fuel is consumed, the fuel level decreases in the tank, or the temperature of the fuel increases due to the effect of increasing the fuel temperature. Some expansion of volume is accomplished without creating harmful high or low pressures in the surrounding environment.

Furthermore, these known facts should not conflict with new safety standards that require a gas-tight plug in the tank at all times, allowing only a small leakage of fuel out of the tank in the event of a vehicle rollover.

The present invention relates to a device placed in a branch pipe attached to a pipe filling a reservoir with fuel, said device consisting essentially of a natural or artificial nitrogen membrane resistant to hydrocarbons, said membrane being having a gap and held between the edges of two concentric cylindrical bodies forming the body of the valve, a play is provided between the membrane and the surrounding edge so that the edge It is avoided that the edges become a source of strain in the membrane that deforms the membrane cracks and unexpectedly alters the flow rate of gas therethrough.

The device described above also determines, for a constant value of high or low pressure inside the reservoir, the same gas flow rate in the opposite direction through the membrane crack.

Furthermore, in the extreme case that the reservoir becomes completely empty, the gasoline pump continues to work for a certain period of time to dry the fuel reservoir.

During this fixed period of time, the pump is generally allowed to pump out an hourly volume of air that far exceeds the volume of gasoline that would be removed.

This results in a relatively large pressure drop within the tank.

This is because the membrane cracks are accommodated for the exchange of gas corresponding to a normal drop in fuel level, which, as mentioned above, takes place with very little emissions.

This unexpected pressure drop leads to rupture of the reservoir.

Also, it is undesirable to extend these cracks to increase the amount of waste allowed to pass through the membrane.

This is because an increased permeability to the fuel also results in the case of vehicle welding.

The invention constitutes a first variant of an improved device which eliminates the disadvantages as mentioned above, whereby a limited flow is conserved in the opposite direction, consistent with the safety standards currently in force. However, an excessive pressure drop in the reservoir is avoided by allowing asymmetric introduction of a large gas flow rate from the outside towards the interior of the reservoir, which is equal to or greater than the displacement of the air-breathing gasoline pump. Ru.

Such a result is achieved in that the edges of the membrane-receiving member do not have central openings of equal diameter.

On the contrary, the side openings of the reservoir are of a larger diameter than the opposite openings.

Thus, when there is pressure inside the reservoir, the membrane is supported on the edge of small diameter and only the central part of the crack that remains free acts, so that the flow rate of fluid outside the reservoir is lower than that of the edge. Determined by the diameter of the openings in the membrane, which is slightly less than the imposed standard - if the internal pressure base is large, the membrane will have an edge opening of large diameter, as described above for when a gasoline pump draws air. Placed on top, the entire split day is allowed to flow and a significant amount of flow is allowed to avoid harmful pressure drops within the reservoir.

The diameters of the two edge openings considered here are calculated according to the ratio of the flow rates provided in the two directions.

In a second variant of the invention, when approaching a membrane with one or more cracks in the interior of the valve body, the one bearing on which the membrane is supported is partially disposed of when the reservoir is under excessive pressure. This has the effect of neutralizing a portion of the crack and limiting the flow of gas through the membrane to a predetermined value.

The invention will now be explained in detail with reference to the drawings of its embodiments, which are shown in a non-limiting manner.

As shown in the first diagram, the reservoir is filled with fuel via a tube 3 whose upper end is closed by a gas-tight frame 4 until level 2 is reached.

One branch pipe 5 is equipped in its free part with a valve 6 according to the invention.

The valve 6 is shown in detail in Figures 2 and 3.

This valve essentially consists of a membrane 7 held between two concentric cylindrical bodies 8 and 90 forming the body of the valve.

The membrane 7 is made of a natural or synthetic elastomer that is resistant to gasoline, and its thickness is such that the membrane retains adequate flexibility within it, yet has sufficient durability consistent with its functions as described below. It is as if it is given.

Such results are obtained by using membranes as thick as 5/10 mm.

The valve body 8-9 is preferably obtained by molding a synthetic material of the polypropylene type.

The outer circumference of this valve is small.

Its outer diameter and length are both approximately 14 mm.

The end of the cylinder 8-9 close to the membrane 7 is bent to form a seat for the membrane.

The membrane is mounted inside the valve body with an axial play of 5 to 10 mm and a small radial play of the order of 3 to 4/10 mrrt.

This is to eliminate strains within the membrane caused by local deformation of their edges following tightening between the cylinders 8-9.

As shown in Figure 3, the membrane 7 is provided with a plurality of cracks with adjacent ends, which cracks are opened under the influence of high pressure acting on one of the surfaces of the membrane.

This illustration is in no way limiting, but was chosen in contrast to others that give less good results.

The membrane 7 is provided with one first crack 10 passing through its center and two cracks 11 located on a diameter perpendicular to the diameter containing the crack 10, which cracks 11 form a first crack 100.
They are provided on both sides with a distance of about Iynm.

The length of these cracks is adapted to the flow rate of gas that has to pass through the membrane (of the order of 35 liters/hour), and in the embodiment shown in the third figure 2.5 mm is preferred.

As mentioned above, due to the absence of strain inside the membrane 7 and the freedom of the membrane obtained by the axial play, the crack 1
011 always retains the same passage area and thus retains its permeability characteristics unchanged relative to what was originally defined.

If the peripheral edge of the membrane is tightened between the valve components 8-9, i.e. installed without any play, the membrane will be deformed and the crack will be unexpectedly large. .

Therefore, it becomes difficult to control the amount of gas exchange through the cracks, which is necessary for good operation of the reservoir.

On the other hand, additional safety is obtained from the above-described device according to the invention.

That is, if a sudden high pressure or pressure drop is induced, the membrane can escape from its seat after appropriate deformation, as shown in Figure 4.

Thus, destruction of the reservoir is avoided in this device.

Finally, taking into account the mechanical properties of the membrane, it can be concluded that during a vehicle rollover, the mere pressure of the fuel is insufficient to significantly open the edges of the membrane crack, resulting in a small flow of liquid (3
of the order of 0i/hour).

In a first variant shown in FIG. 7, the valve is constituted by a membrane 20 placed between two concentric cylinders 21-22 forming the body of the valve.

The membrane is positioned within a branch pipe of the reservoir tube such that the surface of the membrane 200 located on the left side of FIG. 7 receives the internal pressure of the reservoir, while the surface of the membrane 200 located on the right side receives atmospheric pressure. There is.

As in the previously described device, the membrane 20 is made of a gasoline-resistant elastomer and has a thickness of 5/1
It is 0mm.

Similarly, the parts 21-22 of the valve body are preferably obtained by molding a synthetic material of the polypropylene type.

In this device, the feature of the present invention is that the membrane 20
The edge 23-2 of the member 21-22 constituting the supporting portion
4 in that they do not have central openings of equal diameter.

Thus, the opening on the reservoir side (left side in Figure 7) has a larger diameter than the opening on the opposite side.

Another feature of this improved device is that the exchange of gases on both sides of the membrane takes place through one membrane whose length corresponds at least to the diameter of the opening in the edge 23.

As in the previously described device, the membrane 20 is
It is mounted between the edges 23 and 24 with an axial and radial working play of the order of mm.

The operation of the valve in this device is as follows: (1) In the case of high pressure in the reservoir, the membrane 20 is supported with the edge 20 on the edge 24 (position A).

Only the free central part of the fissure 25 is active (.

The flow rate of fluid outside the reservoir is therefore determined by the diameter of the opening in edge 24 and is as small as the imposed specifications.

(2) As mentioned above about the gasoline pump absorbing air, if the pressure drop in the tank is significant, the membrane 2
0 is supported on the large diameter opening of the edge 23 (position B).

The cracks 25 work all over and a very large amount of flow occurs,
Avoid any harmful low pressure in the tank.

The diameter of the openings in the edges 23-24 is calculated according to the ratio of the flow rates carried out in both directions.

The variation shown in FIGS. 9 and 10 is adapted to the three-slit membrane 70 system of the device shown in FIG.

The two concentric cylinders 21 and 22 shown in Figure 7 constitute the body of the valve and are arranged in a branch pipe of the reservoir pipe, similar to those already described, and are made of molded polypropylene. preferable.

The edges 23' and 24 of the members 21-22 also define apertures 30-31 of different diameters, with the diameter of the aperture 30 on the reservoir side (left side in FIG. 9) being larger than the diameter of the aperture 31 on the opposite side. .

In the variant shown in FIGS. 9 and 10, the membrane 7 of elastomer, which is resistant to gasoline,
0 and 11 and with a slight working play, the edge 23
' and 240.

The essential feature of this variant is that the free circumference of the edge 23' is provided with a cutout part 32, the diameter of the bottom of the cutout 33 being larger than the diameter of the membrane 7, so that the edge 23'
There is a radial play 34 between the area consisting of and the membrane.

The operation of the valve described above is carried out in two end positions A and B in FIG.
(1) When the pressure inside the reservoir is high, the membrane 7 occupies position A,
Simply the cracks 10 and 11 provide gas exchange on both sides of the membrane.

(2) When the pressure inside the reservoir is low, the membrane 7 occupies position B.

In this case, a passage formed by the radial play 34 between the periphery of the membrane and the bottom of the cutout is added to the crack 10-11, which reduces the flow rate of gas going in the direction of the bath under low pressure. will be increased.

In a second variant of the invention, shown in FIG. It is made up of one film 40 that is made of aluminum.

This device is placed in a branch of the reservoir tube such that the surface of the membrane 400 located on the left side of the figure is exposed to the internal pressure of the reservoir, and the surface of the membrane located on the right side of the figure is exposed to atmospheric pressure.

As in the device shown in Figure 1, the membrane 40 is made of a gasoline resistant elastomer and has a thickness of 5.
/10mm.

Likewise, the parts 41-42 constituting the body of the valve are made by molding a synthetic material of the polypropylene type.

Unlike the device of the first variant, the membrane moves between the edges of concentric members 41-42 of equal diameter.

In this variant, inside the cylinder 42 and close to the membrane 40, a grid 43 is provided, which serves as a support for the membrane when the reservoir is at high pressure (position B/). work.

Diametrical cracks 44 across the entire thickness of the membrane provide an exchange of gas proportional to the curvature of the membrane.

Depending on the desired effect, the flow rate is lower at position B' than at position A', where there are no obstacles limiting the curvature of the membrane.

In the device shown in FIGS. 13 and 14, the grid has been replaced by cruciform posts, as is evident from FIG.

In this case, the membrane comprises a group of fissures arranged to trisect the sector-shaped cavity defined by the cruciform struts 45.

As in the previous case, this device is used when there is high pressure in the reservoir (
Restricting the movement of the membrane to position B'), the gas flow rate is therefore also restricted compared to when the membrane is at position A'.

However, for very high pressures, additional deformation of the membrane is induced because it fits into the fan-shaped cavity defined by the cruciform struts.

This results in a wide opening of the cracks and an increase in exchange gas.

Therefore, this device works at multiple stages of pressure.

In FIGS. 15 and 16, the membrane 40 is supported on a concave septum 46 with through holes when there is pressure in the reservoir (position B') so that gas exiting the reservoir enters the cracks described above. It is discharged through the through hole via a similar membrane crack.

This device provides an asymmetrical deformation of the membrane which induces different flow rates determined by the membrane occupying position A' or B'.

The device shown in FIGS. 17 and 18 comprises a convex bearing bulkhead 47 on which a membrane 40 is placed and undergoes original deformation under pressure corresponding to the permissible gas flow rate.

At low pressure in the reservoir (position A'), the membrane 40 undergoes an identical but much larger deformation, allowing a predominant flow rate.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a storage tank equipped with a safety device according to the invention, FIG. 2 is a longitudinal sectional view of a safety device according to the invention, FIG. 3 is a surface view of a membrane forming part of the safety device, and FIG. Figure 4 is a longitudinal sectional view of the safety device when the membrane is in its terminal position; Figures 5 and 6 are longitudinal sectional views of the deformation device and a surface view of the device;
and FIG. 8 is a view similar to FIGS. 5 and 6 showing another modification of the present invention, FIGS. 9 and 10 are longitudinal sectional views and surface views of a safety device having a membrane support constituted by a grid,
Figures 11 and 12 are views similar to Figures 9 and 10 in which the membrane support is a cruciform member; Figures 13 and 14 are views 9 and 10 in which the membrane support is a concave septum with a through hole;
Figures 15 and 16 are similar to Figures 9 and 10 in which the membrane support is a convex partition with through holes. 1...Storage tank, 3...Pipe, 4...
・Airtight frame, 5...branch pipe, 6...valve,
7,20,40...Membrane, 8°9.13,21.
22, 41, 42... Cylindrical body forming the body of the valve, 10, 11, 25, 44... Crack in the membrane,
14...Ball, 15...Float, 16...
...pin, 23.24 ... end edge of cylinder,
32... Notch part, 43... Lattice,
45...Cross strut, 46...Concave bulkhead, 47...Convex bulkhead.

Claims (1)

[Claims] 1. Safety devices for ventilation of automobile fuel tanks:
a hydrocarbon-resistant natural or artificial nitrogen membrane is held between the edges of two concentric cylinders forming the body of the valve, with at least one through-slit;
play is provided between the membrane and the surrounding edge;
As a result, the edge becomes a source of strain within the film,
An arrangement characterized in that the cracks in the membrane are deformed to avoid unexpected changes in the flow rate of gas passing therethrough.